Geometric Frustration in Buckled Colloidal Monolayers

Frustration collage showing microscope image of underlying striped and zig-zag patterns that form to relieve sample frustration. Also illustrated are various tiling configurations of isosceles triangles in the plane that help to explain observed structures.

Frustration is a feeling known to anyone who has had to choose one course of action from a range of imperfect options. Interestingly, similar situations arise in nature, and scientific ideas about frustration have been explored to understand materials as varied as water, ceramics, magnets and superconductors. Geometric frustration in condensed matter arises when the geometry of the crystal lattice prevents minimization of local interaction energies. This multiplicity of imperfect choices leads to frustrated media with bizarre properties such as many ‘lowest energy’ states wherein small perturbations cause giant property fluctuations, and entropy at zero temperature that grows with sample size. Since the experimental scenario emulates classic models of spin frustration, the research builds a novel bridge between two very different fields of materials science: soft matter and frustrated magnetism.